Superregenerative system for receiving angular-velocity-modulated wave signals



May 5', 1953 D. RICHMAN 1 SUPERREGENERATIVE SYSTEM FOR RECEIVING ANGULAR-VELOCITY-MODULATED WAVE SIGNALS 3 Sheets-Sheet 1 Filed June 25. 1948 GENERATOR MODULATED OSCILLATION FREQUENCY- AUDIO- FREQUENCY Time FIG.4

l oua ac uvmvroa. DONALD RICHMAN BY Q y ATTORNEY May 5, 1953 D. RICHMAN SUPERREGENERATIVE SYSTEM FOR RECEIVING ANGULAR-VELOCITY-MODULATED WAVE SIGNALS I5 Sheets-Sheet 5 Filed Jim 25. 1948 Bi AU DIO- FREQUENCY AMPLIFIER FlG.9

INVENTOR. DONALD RICHMAN 2% fli ATTO RN EY AUDIO- FREQUENCY AMPLIFIER Patented May 5, 1953 UNITED STATES OFFICE 2,637,807 sUrERnsoENER-Anvn sYs'rEM FDR ans. Q VING NGULA ELQQ Y MDDU? LATED WAVE S GNALS I Donald Riclnna-n, Flushing, N. Y., assignor to fiaze ine Research, Inc,

r icn of nois Chicago, 111,. a. er-

21 Claims... 1

The present invention is directed to wave-signa l receiving systems of the superregenerative type which are particularly suited for the reception of angular-velocity-modulated Wave signals. The expression angular-velocity-modulated wave signal is used in the present specification and appended claims in a generic sense to define a Wave signal which is either frequency or phase modulated in accordance with the intelligence to be conveyed. However, since frequency modulation is the more usual form of transmission, the invention will be described in detail in that connection.

It is well understood that a superregenerative receiver comprises a regenerative oscillatory cir-' cult and a quenching arrangement. The latter constitutes an integral part of the regenerative circuit in the case of receivers of the selfquenching type or constitutes a separate signal source coupled to the regenerative circuit in the tions that are quenched or damped in the next succeeding interval of positive conductance. The

oscillations which are thus periodically produced have a characteristic, such as an amplitude char.-

acteristic, which manifests the modulation of a received Wave signal at the time the oscillations are initiated. Those oscillations may be utilized in any of several well-recognized methods to derive the modulation-components of the received signal.

The use of such a receiver in the reception of amplitude-modulated waves is exceedingly Well' known at the present time. In general, the

quenching frequency is selected to be low rela tive to-the oscillatory frequency of the regenerative circuit but at least twice as high as the highest frequency-modulation component to be" accommodated. In operation, the amplitude variations of the received signal control the oscillation peak amplitude or the duration of the; peak oscillation interval in each quench cycle so that an output signal obtained from the receiver manifests the modulation components of the received signal.

it is also known that super-regenerative re ceivers may be employed in the reception of ire- If such a r'e-' quencwmodulated wave signals.

ceiver'is side-tuned to the mean frequency of I the frcquency-modulated signal, the frequency excursions are converted to amplitude variations inview of the sloping response which is characteristic of side-tuned operation. Having eifected a-conversion to amplitude modulation, the receiver may function in a manner generally similar'to that explained above to derive the desired modulation components'oithe received signal. Sincethe receiver is primarily responsive to amplitude variations of the applied signal, undesired amplitude modulation superimposed on the received frequency-modulated signal will, of course, be derived'with the frequency modulation components.

' The presentsinvention concorns'a novel superregenerative system-for receiving a; frequency.- modulated wave signalxand exhibiting improved amplitude-modulation rejecting properties. The invention is. related to. the inventiondisclosed and claimed in a concurrently filed application of BernardflLoughlin, Serial No. 35,257, ontitled FAnsularevelocityrModulation Wave-els al anslat ne System? nowPatent 2, 13,316 grantedoctober "I, 19.52; This patent describes a superregenerative system for translating a an ularwel cityrmodulated wa eusis al and for Qbtainin the modulation components ther of by ns ap ase 911 1 i on ef ected n a 11.- DQ. 38.63 21? W b lQQlil fl li pg nidetect r i aist ine i the recei ed si nal s enaehase eie e. .s snal- In the a t ju t men one the p a e-defls cmrrised by t e resi u scillaio s in the surerreeenera ve detec or which i th s nstance has smell dampi g: tha c at ns of on qu nch cy le rry. o e to the n qu n h cycle. n the nsta t rra ement, a cont nu us-Phase .reiercnce s nal is supplied by a separat sig l generator.

The system toe d cri ed is a o c se y sted-to thev su ject matter f a pli an s urrently. fi ed applica icnificr m Na $5 43, antitledfSup i-r sencrat vefiystem for Re eivin Angular elocityrlylo ulated Wave Sig als. ot ten zfififi' fi g anted O ob r 9.5 s patent derives the modulationcomponents of an angular-veincity-modulated signal by comparing 7 the phase of the received signal, as manifested bythe signal output of a superregenerative amplifier, with that of a continuous-phase reference signal supplied'by-a signal generator including a blocking oscillator which has hang-over or residualoscillations endur n throughout each blocking interval; In Ratent2,6l3,3l5, the phase comparison is made in a phase detector separate and distinct from the super regenerative stage, whereas in the present application the phase comparison is effected within the superregenerative amplifier.

It is an object of the present invention to provide a new and improved superregenerative system for receiving an angular-velocity-modulated wave signal.

It is another object of the invention to provide a superregenerative system, for receiving an angular-velocity-modulated wave signal, having improved amplitude-modulation rejecting properties.

It is a further object of the invention to provide an improved system for receiving an angular-velocity-modulated wave signal in which the desired modulation components are derived by virtue of a phase detection action accomplished within a superregenerative' receiver.

It is an additional object of the invention to provide an improved system for receiving an angular--velocity-modulated wave signal in which the desired modulation components are derived by a phase detection or comparison performed during periods of maximum sensitivity of a superregenerative receiver.

It is another object of the invention to provide a system for receiving an angular-velocity-modulated wave signal in which the desired modulation components are derived by a phase detection or comparison which takes place in a superregenerative receiver during intervals when the oscillations generated in the receiver have achieved a high amplitude level.

In accordance with the present invention, a system for receiving an angular-velocity-modulated wave signal having a. given mean frequency comprises an oscillation generator for supplying a continuous-phase reference signal having a frequency different from that of the aforesaid mean frequency. The system includes a superregenerative wave-signal phase detector for utilizing the angular-velocity-modulated signal and phasereference signal. The system also includes means.

for applying the phase-reference signal to the detector at least during a selected interval of each quench cycle of the detector; The detector is center-tuned for signals of the aforesaid mean frequency and side-tuned for the phase-reference signal and is responsive to both of the last-mentioned signals during the aforesaid selected in-' tervals of the quench cycles to effect therein a phase comparison of the angular-velocity-modulated signal and the phase-reference signal to develop an output signal having characteristic variations representing the modulation components of the angular-velocity-modulated signal. Additionally, the system includes means responsive to the phase relations of the angularvelocity-modulated signal and the phase-reference signal during the intervals of phase comparison for controlling an operating characteristic of the system to tend to maintain a substantially fixed apparent phase relationship between the angular-velocity-modulated signal and the phase-reference signal.

In accordance with one mode of operation of 4 method of practicing the invention may be termed a low-level phase detection.

In accordance with an alternate mode of operation of the invention, the phase comparison occurs after the oscillations of the superregenerative receiver have achieved an amplitude level that is relatively high even though it may be less than saturation-level amplitude. This latter method of practicing the invention may be considered a high-level phase detection.

' For a better understandin of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings, Fig. l is a circuit diagram, partly schematic, of a complete system for receiving an angular-velocity-"nodulated wave signal and embodying the present invention in one form; Figs. 2a-2d include vector diagrams and curves utilized in explaining the operation of the Fig. 1 arrangement; Fig. 3 is a schematic representation of a system generally similar to that of Fig. 1 but including the invention in modified form; Fig. 4 is a curve utilized in explaining the operation of the Fig. 3 arrangement; while Figs. 5, 6, '7, 8, and 9 represent further Wave-signal receiving systems embodying additionally modified forms of the present invention.

Referring now more particularly to Fig. 1, the system there represented is adapted to receive and translate an angular-velocitymodulated wave signal, such as a frequency-modulated carrier-wave signal. This system, as will become apparent from the explanation hereinafter of its mode of operation, is a type of low-level superregenerative phase detector in accordance with the present invention. The frequency-modulated signal to be translated i indicated as originating in a source II] which may comprise an antenna system for intercepting a signal transmitted from a remote transmitting station. This signal will be considered as having a given mean frequency.

As previously indicated, the present invention contemplates deriving the modulation components of the received frequency-modulated signal by a process of phase detection accomplished within a superregenerative circuit and to that end the over-all receiving system comprises a phase-reference oscillation generator H for supplying a continuous-phase reference signal. The expression continuous-phase reference signal as used here and in the appended claims is intended to denote a signal that has continuity of phase and a phase that is not directly affected by" the received frequency-modulated signal. However, the reference signal need not necessarily be uniform in amplitude and need not necessarily have a constant frequency. It will be evident in discussing other specific modifications of the invention that the phase-reference signal, while being of continuous phase, may have relatively high and relatively low amplitude levels in alternate operating intervals of the generator H and further-its frequency may be varied by a control potential in a manner related to the modulation of the received frequency-modulated signal for a purpose to be described hereinafter. Nevertheless, the expression continuous-phase reference signal is not intended to describe the signal generated in a superregenerative amplifier having carry-over" and used to amplify the received frequencymodulated signal. A superregenerative amp1iacrea e fier is said to have carryover when the dampin is such that the oscillations generated in one quench cycle carry over and have an appreciable amplitude at the start of the nextsuoceeding quench cycle. In the remaining discussion of the Fig. 1 arrangement, it will he assumed that generator it supplies a continuous-wave signal having a frequency different from the mean frequency of the received frequency-modulated signal but having an effective intensity that is very large compared with that of the received signal.

The over-all receiving system additionally comprises a superregencrative Wave-signal receiver for making a phase comparison of the frequency modulated signal from the source it and the phase-reference signal from the oscillator ll during a selected interval of each quench cycle of the superregenerative receiver to develop an output signal having characteristic variations representing the modulation components of the frequency-modulated signal.

In order to avoid confusion, the superregenerative receiver Will be referred to hereinafter as a superrcgenerative phase detector and, shown in Fig. 1, it is of the self-quenching type. It is comprised of a triode type of vacuum tube l2 arranged in the circuit of a C'olpitts oscillator. The resonant frequency-determining circuit ineludes an inductor it, a damping resistor it, and condensers l5, l6 and ii. One terminal of the resonant circuit is directly connected to the anode of the tuhe l2 and its opposite terminal is eilectively connected to the control electrode thereof through a condenser til. is connected to the junction of condensers i5 and it and is grounded. through a signal-drequency choke coil iii. The parallel combination of a.v condenser is and a resistor it connected to the control electrode is a quench-frequency stabilizing network of a type disclosed and claimed in applicants copending application Serial No. 788,765, filed November 23, 1947, entitled Self-Quench Superregenerative Receiver, now Patent 2,616,039, issued Gctooer 1952. The values of the components 2! and 2! may be chosen so that the network has a low impedance to audio frequencies to avoid audio degeneration.

Included in the phase detector is a. selfquenching arrangement comprising means re.- sponsive to the phase relations of the compared signals for controlling an operating characteristic of the over-all system. Specifically, the quench frequency of the phase detector is controlled to tend to maintain a substantially fixed apparent phase relationship between the received frequency-modulated. signal and the phase-reference signal. The particular self-quenching arrangement used is known as an anode-circuit resonant quenching network, fully described and specifically claimed in a related application of Donald Richman, Serial No. 28,595, filed May 22, 1948, and entitled Self-Quench Superregenerative Amplifier. It comprises the condenser 17 connected in a series circuit with an inductor 22, a decoupling resistor 23, and a source of unidirectional potential +3. The series circuit may have a resonant frequency approximately equal to one-half of the self-quenching frequency desired to be established in the phase detector.

To effect a phase comparison, the frequencymoclulated signal source it is coupled to the resonant circuit i3--il through a coupling con-- denser 24, and the oscillation generator l l is like- The cathode ca wise couple o t e res nan circuit through a: on nser 25.

A iurth r coupl n condenser 2E and a filter network, comprising series resistors 2-? and shunt condensers ZB-and til-couple audio frequency amplifier 3! to the resistor there by to apply output signal from the phase detector to the audio-frequency amplifier. The amplifier may include any desired number of stages, and a sound-signal reproducing device 32 is coupled to its output terminals.

In considering the operation of the described arrangement, it is convenient initially to refer to the superregenerative action or the phase detector including the tube I2. one element of the resonant circuit which inludes the inductor 22 and is char ed throueh the latter; Byvirtue of the resulting resonant charging of the condenser, the potential developed thereacross may achieve a value anpreaching twice that of the unidirectional source +13. With the condenser ,1! charged, an excitation potential is applied to the anode cathode circuit of the tube 12 to render that tube conductive. During its conductive interval. which corresponds to the characteristic nesative-conducs tance interval of a superre cnerative receiver, oscillations are produced in theoscillatory circuit ate frequency d termined by the resonant circuit l3l'|. As the oscillationsare generated, the condenser i1 is discharged reducing'the anode excitation potential of the tube. When'the tube is rendered nonconductive, the circuit. enters upon an interval of positive conductance and the oscillations previously generated are quenched. Thereafter, the condenser ii is recharged preparatory to the generation of oscillations in the next quench cycle. Except for the resonant feature of the self-quenching network, this is I characteristic self-quench superreeenerative operation. The quenching frequency is low relative to the oscillatory frequency or" t c superegenerator but is at least twice as high as the highest modulation-frequency component to be detected.

In utilizing the superregenerative circuit as a phase detector, as contemplated by the present invention, the frequency-determining circuit is tunable so that the received frequency-modulated signal and the phase-reference signal may jointly determine the response of the detector. As shown, the inductor 13 is adjustable and the tuning characteristic is indicated in Fig. 2a. For the specific case under consideration, the oscillatory frequency of the superregenerative phase detector is approximately equal to the mean frequency of the frequently-modulated signal and the acceptance band of the detector includes the frequency of the phase-reference signal. EX- pressed differently, the phase detector is approximately center-tuned to the mean frequency Fs of the frequency-modulated signal and is sidetuned to the frequency F of the phase-reference signal supplied by the oscillator Ii. The manher in which a phase comparison of the frequency-modulated signal and the phase-reference signal is eifected in the phase detector including the tube l2 willbe explained with reference to the Vector diagram of Fig. 2b.

Any signal applied to a superregenerative circuit may be considered to be effective to produce a transient at the oscillatory frequency of that circuit. Thus, for the case under consideration, the received frequency-modulated signal and the phase-reference signal individually cause a The condenser i1 8' 7. transient to be produced in the superregenerative circuit including the tube l2. The relative amplitude of the transients is determined jointly by the selectivity characteristic of the superregenerative circuit and the relative amplitude of the signals causing the transients. Similarly, the relative phase of the transients is related to that of the signals producing the transients at the period of maximum sensitivity.

Referring now to Fig. 2b, the vector Vo represents the transient produced by the phasereference signal from the oscillator I while the transient produced by the frequency-modulated signal is represented by the vector Vs rotating about the vector V0. With the received frequency-modulated signal and the phase-reference signal continuously and concurrently applied to the phase detector, the response of the detector in any quench cycle is governed by the effective signal amplitude in its resonant circuit s l3-l1 at the period of maximum sensitivity.

Maximum sensitivity occurs in every quench cycle at the time when the conductance of the phase detector has an approximate zero value in a transition from positive to negative conductance. For the phase relations indicated by the vectors V0 and Vs in Fig. 2b, the effective signal amplitude at the interval of maximum sensitivity is indicated by the resultant full-line vector VE Since the oscillations generated in any quench cycleof the phase detector have an initial amplitude related to that of the effective signal amplitude Vs, the time at which the oscillations achieve saturation-level amplitude after the initiation of a quench cycle is controlled by (and the selfquenching frequency is established in accordance with) the effective signal amplitude. If the relative frequencies of the phase-reference signal and the frequency-modulated signal are such that the same phase relations denoted by the vectors V0 and Vs are present at each maximumsensitivity period of the superregenerative phase detector, the self-quenching frequency is maintained at a fixed value.

Due to the frequency modulation, it'will be apparent that, in generaL'the rate of rotation of the vector Vs relative to the reference vector V0 varies. For the condition in which the received signal vector Vs has advanced to attain the position shown by the broken-line vector Vs at a maximum-sensitivity period of the phase detector, the change in relative phase causes the effectl "e signal amplitude present in the resonant circuit 3-H of the phase detector to be represented by the broken-line vector Vs. This indicates an increased effective signal amplitude as compared with the vector Vs. An increase in the effective signal amplitude causes the oscillations generated in the phase detector I2 to achieve saturation level earlier in the quench cycle and increases the self-quenching frequency. Since the self-quenching frequency has increased, the signal vector Vs will not have advanced as far ahead of the position of the vector Vs by the time the maximum-sensitivity period occurs in the next quench cycle. In other words, the selfquenching frequency varies in such sense and to such extent that it tends to cause the period of condition is encountered due to the-frequency 8 modulation in which the maximum-sensitivity period of the phase detector occurs when the frequency-modulated signal has an apparent phase relative to the phase-reference signal shown by the dash-dot vector Vs" of Fig. 2b. For that condition, the effective signal amplitude Va is less than the first-described effective signal amplitude Vs. The reduction in effective signal amplitude slows down or reduces the self-quenching frequency. This delays the next maximum-sensitivity period of the phase detector so that the apparent phase relation of the frequency-modulated signal and the phase-reference signal approaches a given value, such as that shown by vectors V0 and Vs, at the next maximum-sensitivity period. Thus, it will be seen that the change in self-quenching frequency under the assumed conditions here also tends to restore the apparent phase relationship of the frequencymodulated signal and the phase-reference signal to a predetermined average value, for example that indicated by the vectors Vs and V0. The change in quench frequency is inherent and is automatically obtained in the self-quenching superregenerative phase detector.

The described variation in quench frequency tending to maintain a desired apparent phase relation of the compared signals (the frequencymodulated signal and the phase-reference signal) will be recognized as a function quite analogous to that of the conventional automatic-frequencyeontrol system except for the fact that the latter seeks to maintain a fixed frequency relation. However, in neither case is the desired end result precisely attained because some slight differential is required to continue the control. Nevertheless, the control does seek to restore and preserve prescribed relations as explained.

As shown in Fig. 2b, the apparent phase relation of the compared signals is controlled so that, on an average basis, they have a quadrature phase relation. The control may, if desired, tend to establish a different specific apparent phase relation but the quadrature relation is usually preferable because with it the receiver exhibits its maximum handling capabilities.

It is evident from what has been said that the phase detector including the tube l2 makes a phase comparison of the frequency-modulated signal and the phase-reference signal during the maximum-sensitivity period of each quench cycle and automatically adjusts its self-quenching frequency in accordance with their instantaneous phase relationship. The phase relationship of these signals from one phase comparison interval to the next varies in accordance with the frequency modulation of the signal received from the source l0. For that reason, the variations in the self-quenching frequency represent the modulation components of the angular-velocity-modulated signal. The average anode-cathode current of the tube I2 is directly related to the quench frequency and, therefore, may be utilized to derive an output signal having amplitude vari- 7 The modulation components, after amplification a'asaao-r 9 in the. amplifier 3 l, are. reproduced by the. sound reproducing device.

As previously explained, the: phase relationszof the frequency-modulated signal "and the phase reference signal during the intervals of phase comparison control the" self-quenching frequency" of the phase detector. The change in quench rrequcncyis in a direction tending to establish a predetermined average phase relationship at the maximum-sensitivity periods, such'as that indicatecl by the vectors VS and V0. Viewed onan average basis, this apparent phase relationship is maintained substantially fixed although-at any particular maximum-sensitivity period the phase relationship may deviate in QCCOTdQIlCBiVl/lthllh rate of change infrequency of the trequencymodulated signal-relativeto the phaseueierencc 7 signal.

As -the instantaneous frequency of theirs; quency-modulated signal changes in accordance with the modulation which it conveys, the signal may produce an effective signal amplitudenaving'anyvalue within a range denoted by the. on ole O of Fig. 2b.- Stable conditions resultxwhen the locus of the efiective' or resultant signal vector is represented by thefuu-line portionor the circle 0 because the automatic change in quench frequency occasioned when the locus of the effec-- change in quench frequency is in a regenerative sense to adjust the s stem to its stable operating condition. automatic quench frequehc'y variations realised in the superregenerative phase detector which seek to maintain the desired fixed apparent phase relationship of the frequency modulated signal and the phase-reference sigml, and which alwa s occur in the proper'sense to keep the system in its stable condition, are highly desirable because such operation avoids phase ambiguities. No anulo'iguity arises so long as the over-all system operates in its stable condition.

The described arrangement inherently rejects low-frequency amplitude modulation which may be superposed on the fre uency-modulated signal. The system exhibits this property because on an average or long termbasisthe automatic adjustment of the self-quenching frequency to bythebrolcen-line vector VEA'.

V6, vsrand'vurepresent the phase-reference sigrial,theifrequency modulated signal and the effective signal. amplitude of the phase detector, respectively. Amplitude modulation superimposed on theirequency-modulated signal may, in thexextremcs; add in phase or out of phase with the'frequency modulated signal. Where an in- .ph'aseirelation ispresent, the signal vector Vs hasah added length so that the effective signal amplitude for the phasedetector is represented For the out-cfphase condition, the signal vector Vs is decreased arid the,effectiveisignal amplitude for the phase detector is represented by the dash-dot vector Vow. Solong as the effective amplitude of the phaseereferencesignal. is very much larger than thatofthe frequency modulated signal, as indicatedrin Fig; 2c, the change in amplitude of the effective signal represented by the vectors VE', vm andvm is not appreciable and the ampli: tude" modulation thus hasaninappreciable effect in. changing the ,self quen'ch frequency of the phaseidetectom The arrangement is, according- 1y, insensitive to amplitude modulation superimposedzaon thetrequencwmodulated signal.

Itimustbe realized that the references to the intensity or amplitude of the phase-reference signalare-directed to thein-tensity of that signal as it appears in view of the selectivity of the phase detector as distinguished from the amplitudetmeasured at the output terminals of the oscillation generator H. Sincethe phase detector is side'tuned to thephas-reference signal, the signal amplitude produced by the generator H must-be slected'to take into consideration the frequency-response characteristic of the detector.

For the urposeof explanation, the operation 'ofthe l arrangement may be viewed a little stabilize andv maintain a fixedapparentphasei'elation of the frequency-modulated signal and the phase-reference signal in maximum-sensitivity periods ell ecti-vely locks the quench frequency to a submultiple or fraction of the frequency difference of the compared. signals. ence of low-frequency amplitude modulation the In the pres- Y apparent phase relation to whichthe system: sta- The vector diagram of Fig. 2c demonstrates the-abilityof thedcscrib edasystem-to reject undesired. thigh-frequency amplitude modulation superimposed'oitithe:frequency-modhlatod5signal applied to the; phase? detection Againthevoctors l differently'byconsidering that the frequencymodulatedsignal from the source it and the phase-reference signal from the oscillator l I produce in the frequency determining circuit of the phase detector a 'composite signal having an envelope modulated at the beat frequency. Such a beat signal is represented in Fig; 2d. The variations in the self-quenching frequency of the phase detector tend to cause the maximumsensitivity'peri' ods of the'detector to occur at a given amplitude-and slope of the beat-signal envelope, as indicated by the broken construction line A-A. This is the stable operating condition for which the changes in quench frequency are degenerative-and areeffective to cause the perlods-ofmaximum sensitivity to occur at corresponding points in each-cycle of the beat signal, assuming the quench frequency to be such that a phase comparison is made in eachcycle of the beatsignal. .If' a lower value of quenchingfrequehcy is used, the phase comparison may be made at every second cycle, every thirdicycle, or someother suchsubmulti-ple of the frequency of thebeat frequen'cy sign-al.- From this it is seen thatthophase detector tends to have a quench frequencywhich is" looked to the frequency of theloeat signs-1.01 to-asubharmonic thereof as mentioned previously.

For convenience, the. arrangement of Fig. 1 has been explained on the premise that the superregenerat-ive' detector is approximately center turied-to'the'modulated signal Fe and side tuned to, thephasmreference, signal F0, as indicated i1i E'18. .2o/. "As apra-otical matter, the system is adiustedliuthatmanner for many installations because frequently the n'iodulated. signal F5115 "relatively weekend" requires the added gain incident to center tuning. Also, peak tuning to .the modulated signal usually provides the best signal to noise ratio. However, other operating conditions are both permissible and useful. For example, the superregenerative detector. may be side tuned in any of a variety of fashions to both signals. The modulated signal may fall on one side of the selectivity characteristic and the phase-reference signal may fall on the other or both may be located on the same side. Usually, the modulated signal is the closer to the peak response frequency of the detector.

When the detector is side tuned to the modulated signal, the locus O in Fig. 2b of the vector Vs is no longer a circle because of the side response effect which introduces an amplitude change in the vector Vs with frequency deviations. The operation of the system is nonetheless essentially as given above. It will be found that for operating conditions in which the mean frequency of the modulated signal is greater than that of the phase-reference signal, best results occur when the stable conditions are about as 'described in connection with Fig. 217. On the other hand, if the mean frequency of the modulated signal is less than the frequency of the phasereference signal, a vector diagram that is the mirror image of Fig. 2b represents the preferred operating condition.

One embodiment of the Fig. 1 arrangement found to have practical utility included the following values of its circuit components which are recited here only by way of illustration:

Tube l2 /2 section of a 12AT7 duo triode.

Resistor l4 8,200 ohms.

Resistor 2i 5,000 ohm potentiometer adjusted for mean quench frequency.

The invention, of course, is not limited to superregenerative phase detectors of the selfquenching type. The embodiment of Fig. 3' indicates schematically its application to a separately quenched arrangement. In Fig. 3, unit 35 is a regenerative oscillatory circuit with which is associated a separate quench-frequency oscillator 35. These two units together constitute a superregenerative phase detector of the separately quenched type. The oscillator 36 comprises means for supplying a quench signal to accomplish superregenerative action. Terminals 31 and 38 represent input terminals coupled to the regenerative circuit and to which the frequencymodulated signal may be applied from any desired source or antenna system. The connection designated AFC from the output terminals of the regenerative circuit to the input terminals of the quench-frequency oscillator denotes an automatic-frequency-control circuit, supplying the modulation-signal output of the phase detector to the quench-frequency oscillator. The oscillator 36 will be understood to include a frequencycontrol system which utilizes the applied automatic-frequency-control signal to adjust the opera-ting frequency of the oscillator to tend to maintain fixed apparent phase relationships between the frequency-modulated signal and the phase-reference signal. The phase-reference oscillator, the audio-frequency amplifier, and the sound-signal utilizing device of Fig. 3 are essentially the same as those of Fig. 1 and are identified by similar reference characters.

This arrangement will be seen to operate in essentially the same manner as the embodiment of Fig. 1. The quench-frequency oscillator 36 may, if desired, be a blocking oscillator and the automatic-frequency-control signal may be applied to the blocking circuit of the blocking oscillator toadjust its blocking frequency, thereby to control the quenching frequency of the phase detectoiv Of course, this adjustment of the quench-frequency oscillator and the resultant control of the frequency of the quenching signal supplied to the regenerative circuit 35 are, as previously described, in a sense to maintain a substantially fixed apparent phase relationship between the frequency-modulated signal and the phase-reference signal.

The significant difference in the operation of a self-quenching superregenerative phase detector of the type shown in Fig. 1 and the separately quenched detector utilized in Fig. 3 may be easily understood with reference to the curve of Fig. 4. This curve is idealized and represents the saturation current pulses appearing in the anode circuit of the regenerator tube of a superregenerative phase detector. There are two time factors which are material and either may vary to cause the average anode current of the detector to vary with the modulation of an applied signal. The first factor, designated TQ, is the period which corresponds to the frequency of the quenching signal and the other factor Tr is the duration of the saturation pulse in a particular quench cycle. The average value of anode current is related to these factors in accordance with the following expression:

where i? is the peak amplitude of the saturation pulse. The self-quenching type of superregenerative detector varies the time interval TQ but maintains a substantially fixed saturation-pulse duration TP. In the separately quenched detector, and in the absence of any frequency control on the quench oscillator, the saturationpulse duration TP varies but the quench period T is essentially constant. It is apparent from Equation 1 that in either case the average anode current of the superregenerative phase detector manifests the influence of amplitude variations of the effective applied signal and, therefore, represents the modulation components derived from that signal. While the self-quench arrangement adjusts its quench ng frequency automatically, the externally quenched system of Fig. 3 utilizes the modulation-signal output of the phase detector as a frequency control for the quench oscillator 36 by which to vary the quench period TQ. 1

n further modification of the invention is represented in Fig. 5 which again util zes a self- .quenching superregenerative receiver 40 as a phase detector. In this modification, a reactance tube, or any. other conventionalfrequency-controllingmeans is-coupled to the phase-reference oscillator H to control .thefrequency' of the phase-reference signal. The modulation-signal output from the selfuenching superregenerative receiver is supplied by aconnection 42 to the input circuit of the reactance tube, thereby to adjust thefrequency-of the phase-reference signal in accordance withthe instantaneof Fig. 1 to derive the modulation com onents of the applied frequency-modulatedsignal. Since the apparentphase relationship-of the frequencymodulated signal and the phase-reference signal isidetermined by the relative frequencies of those signals, the desired, fixed'aoparent phase relationship may also be maintained by controlling their relative frequencies to crush the frequency deviations inherently present when a frequency-modulated signal is'compared with a iixed frequency reference signall This type of control is introduced by the reactance tube 4! which operates so to control the frequency of the oscillator ll thatit tends to follow the instantaneous frecuency modulation of the ire enemy-modulatedsi nal, thus to reduce the relative a parentphase-differences of the signals as between successive intervals of phase-comparison by the phase detector 41 The action of the reactor tube 4'! thus augments the eirect of the automatic variations of the seli-ouen hingfreouenoy of the phase detector as these variations tend to maintain-a constant chase relation between the freouenev-modulated si nal and the reference signal a pearing in the resonant circuit of the phase detector. Thedual control. com-prising variations. inthe self-quench ng freouency of thep-hase detector-andvariations in the freouency ofthe hase-reference signal, increases.- the stabilityoi the system.

Further improvement'inthe operation of systerms of the type previously discussed may be achieved,- bysupplying the treouencyemodulated signal to the phase detector through-an amplitudelimiter whichmay remove; some undesired ampl tude modulation that may bezsu erimp'osed on thatsignah It. mayalsobedesirable to supply the freouencymlodulated si nal through a channel which features-automatic volume control or gain controlso "that'the relative intensities of the frequencywmodulated signal and the phase-reierence signal are maintained at 001mcaratively fixed values. Thus Fig. 6, which illustrates an application of the present invention to a complete television receiving system, features again control to limit the frequency-modulated signal to a relativelyconstant amplitude level.

The television receiver'of Fig. 6 comprises a radio-frequency amplifier of any desired-number of stages hav ng an input circuitcouoled-to an antenna'ground system 5!, 52. Connected in cascade with the amplifier 50 are'an oscillatormodulator 53,. an intermediatedrequency ampliher 54. a detector andautomatic-eontrast.-con- .trol' (AC6) souroe 55 and a video-freouency amplifier and reoroducer system 56. The unit 56 will, be understood to iHGltldfiLQlltt'Ql; metastases of video-frequency amplification, the image-reproducing device, the usual-scanning systemsand the synchronizing-signal separator for supplying synchronizing signals tosuch scanning systems. The automatic-contrast-control potential derived from unit .55 is applied to one or more of the tubes in the-radio-frequency amplifier 50, the oscillator-modulator 53 and the intermediate-frequency amplifier 54 in a conventional manner.

Assuming that the sound signal accompanying .the desired television signal is frequency-modulated, the sound system included in the television receiver may be thesame as that'represented in Fig. 5, corresponding components thereof being identified by similarreference characters. The requency-modulated sound signal may be-;s.1 1-p plied to the sound-signal translating system through the connection extending from the. output circuit of the oscillator-modulator 53 to the input terminals of the self-quench super-regenerative receiver M! utilized as aphase, detector.

Referring briefly to the operation of the systom, the television signals interceptedby theantonne. system El, 52 are selected and amplified in the radio-frequency amplifier 5E! and are delivered to the oscillator-modulator 53 wherein they are converted into .intermediate-frequency signals. The intermediate-frequency signal is selectively amplified in the intermediate-frequency amplifier M, is detected in the detector 55, and the video-frequency modulation components are supplied to the video-frequency system 56 for utilization in reproducing an image conveyed by the received televisionsignal. The automaticcontrast ccntrol potential derived in the unit 55 controls the gain of the units 50, 53 and 54 to ma ntain the intensity of the signal input to the detector 55 Within a narrow range of values for a wide range of received signal intensities.

Sound signalsaccompanying the received television sigrnal are converted bytheunit 53 toa sound intermediate-frequency signalwhich is supplied tothe phase detector iii] wherein, by the process of phase comparison withthe reference signal-from the oscillator H, the sound-modulation components are derived and applied to the audio-frequency amplifier 3!. After amplification therein, the sound'signals are reproduced'by the device 32. Theautornatic-contrast-control connection, by controlling the gain of the radiofrequency amplifier to, the oscillator-modulator 53, and the inter-Inc(hate-frequency amplifier 54 maintains the intensity of the sound intermediate-frequency signal sup-plied to the phase detector so within a relatively narrow range for a Wide range'of received signal intensities.

A particularly useful and compact receiving system embodying-the present invention is represented in 7 and features the use of a blocking oscillator Mas the continuous-phase reference signal source. A blockingoscillator is similar in natureto a superregenerative circuit in that in each oscillations are periodically generated and then damped. Each has a quenching action and itis possible to derive the quenching signal for one'irorn the quenching circuit of the other. That is, the superregenerative circuit may be-seli-quenching and may supply a quenching signal to the blocking oscillator or the blocking oscillator may serve as both: the quench signal source for a separately quenched dete'ctor'and the phase-reference soin'cc. The latter arrange- ;ment is used in the Fig. it-embodiu'xent.

The blocking oscillator it is or the C'olpitts type endincludes a triode vacuum tube ti and 15 an associated frequency-determining circuit 62G5. -Ihe anode of the tube BI is connected to one side of the frequency-determining circuit; the control electrode is coupled through a condenser Bl to the opposite side thereof; while the cathode is connected. to the junction of condensers 64 and 65. The cathode is also connected to ground through a signal-frequency choke coil 88 and a self-quenching network comprising a condenser 69 and a parallel-connected resistor Iii. The network provided by the condenser "II and a resistor 12 in the rid circuit of the tube GI is utilized for stabilization. The damping of the blocking oscillator, effected by the resistor 63, is chosen so that the oscillator has what is known as hang-over. A blocking oscillator with hang-over is one in which the oscillations generated in one conductive interval of the oscillator tube carry over in the tuned circuit of the oscillator to the next conductive interval so I that residual oscillations are present in the tuned circuit throughout each blocking period. Or it may be defined as a relaxation oscillator that has residual oscillations throughout the blocking intervals which intervene the oscillation-generating periods.

The quenching signal to be applied to the re generative circuit 35 to achieve superregenerative action is derived from the blocking oscillator 66. To that end, periodic pulses of potential derived from the periodic pulses of anode current of the tube 6| are applied with a suitable time delay to the quenching circuit of the regenerative unit 35. The delay is derived in a time-delay network comprising series-connected inductors 13, I3 and shunt-connected condensers I4, 14. The input terminals of the time-delay network are coupled to the anode-cathode circuit of the blockins-oscillator tube 6|. Its output terminals are connected to the quenching circuit of the regenerative unit 35 through a stabilizing network provided by condensers I5 and I6 and a resistor Il'. When the regenerative circuit is of the Colpitts type as shown in Fig. l, the network I6, I? may be included in the control-electrode circuit of the re enerator tube and this may be accomplished by having the connection I8 extend to the control electrode of that tube.

With the described connections, a quenching signal which has a frequency corresponding to i the blocking frequency of the oscillator 60 is applied to the regenerative circuit 35. The time relation established by the time-delay network 73, 7A is chosen so that the regenerative circuit 35 exhibits periods of maximum sensitivity during the saturation intervals of the blocking oscillator 60. With that timing relation, there are applied to the regenerative circuit 35 at each period of maximum sensitivity both the frequency-modulated signal and the high-intensity phase-reference signal because the signal output of the oscillation generator so has a high value during its saturation or oscillation-generating intervals. Hence, a phase comparison may be accomplished within the regenerative circuit 35 functioning as a superregenerat ve phase detector in the manner previously described.

In order to maintain a substantially fixed apparent phase relationship between the frequencymodulated signal and the phase-reference signal, the modulation-signal output of the regenerative circuit-is applied to-a reactance tube 4| coupled to the frequency-determining circuit of the blocking oscillator 60 to adjust its oscillatory frequency. At the sametime the modulation-signal output may be applied; after amplification in an amplifier 80, to the grid-stabilizing circuit II, 12 of the tube SI. Since the potential developed in the stabilizing circuit II, I2 in conjunction with that of the self-quenching network 69, "I6 governs the blocking frequency of the oscillator (iii, the added control enables the quenching frequencies of both the blocking oscillator and the regenerative circult 35 to be adjusted concurrently'with the oscillatory frequency of the blocking oscillator. The variations in quenching and oscillating frequencies are chosen to be in a sense to establish and maintain a fixed apparent phase relationship between the frequency-modulated signal and the phase-reference signal.

All of the arrangements considered thus far are of the low-level type in that the phase comparison made in the superregenerative phase detector occurs during its periods of maximum sensitivity; 'When the phase detector is of the selfquenching type, as in the embodiments of Figs. 1, 5 and 6; saturation-mode operation is employed. However, when the phase detector is of the separately or externally quenched type, as in the modifications of Figs. 3 and 7, the phase detector may be operated in either the linear or saturation mode. In saturation mode, the oscillations produced in each quench cycle of the superregenerative detector reach saturation-level amplitude before they are quenched, whereas in linear mode the oscillations are quenched before attaining saturation-level amplitude.

High-level phase detection in accordance with the present invention'is practiced in the embodiments of Figs. 8 and 9. In Fig. 8,' the superregenerative phase detector includes a trlode vacuum tube I00 and a'n'associated frequencydetermining circuit Nil- I05. The frequencydeterrnining circuit is directly connected with the anode of the tube I00 and is coupled to the control electrode thereof through a condenser I06. The junction of the condensers I03 and I04 is connected to the cathode of the tube I09 which is also grounded through a signalfrequency choke coil 01. The stabilizing network associated with the control electrode includes a condenser I08 and a resistor I09 which have values so selected that its time constant effects direct-current and audiofrequency degeneration. That is, this network develops signal potentials in accordance with the direct-current and audio-frequency components of the phase detector. Anode-circuit self-resonant quenching is utilized as in the arrangement of Fig. l, the quenching network including the condenser I 95, an inductor 286, a resistor 20'! and a unidirectional source +13. However, the quenching action of the detector is under the control of and is synchronized with a phase-reference signal generator, as will be made clear hereinafter.

The phase-reference signal is supplied-by a blocking oscillator of the Colpitts type having anode-circuit resonant quench. The blocking oscillator is provided by a triode vacuum tube I l5 and a frequency-determining circuit I i6I23. A stabilizing network IZI, I22 is associated with the control electrode of the tube H5 to stabilize its blocking frequency. The quenching network for the blocking oscillator includes the condenser I26, an inductor I23, a resistor IE I and a source of unidirectional potential +13. A link circuit, including an inductor I25 inductively coupled with the inductor "I I5 and an inductor I25 inductively coupled with the inductor MI of the frequency-determining circuit of the superregencircuit .ilil, 12.6, from thef blockin'gtosci-llator FMS.

email the load circuit "for the diode .r-limiterz'and :th-is load circuit has a discharge timeconstantathat is long as compared with the --saturation-period of the phase-detector. Inrtheimodification under consideration, it is preferred that-thediode limiter be operative during the early v portion .of reach oscillation interval of the -super egenerativephase detector but be disabled for. the final ,p'ortion lot su period nsly, :means are provided for disabling the limiter-preferably during intervalsin which thephasecomparison istobemade. This means includes a condenser .13 which couples the load circuit l'3'2, 1'33 of the diode limiter its to the self-quenchingnetwork of the blocking oscillator ill-Etc derive a blocking potential for the diode in response to and'in a fixed time relation with thesaturationinterval, ofithe blockingoscillator lib. It will become clear presently that pulsing oi the diode L30 from the oscillator H 5 and through the-described circuit permits that oscillator to exertacontrol over. and synchronize the quenching .offlthe detector.

In order to establish a substantially apparent phase relationshiplbetween thefrequencymodulated signal and the phase-reterence signal, the arrangement of Fig. 8 contemplates iadjust ment of the blockinglrequency of the blocking oscillator H5 as well .as adjustment of its oscillatory frequency although either one may ,be utilized alone. Adjustment of the blocking frequency is accomplished by a lcathodeiollower 113.5 which is coupled across the resistor T201 ioftthe phase detector through .a condenser 'l'3fi an'dqa resistor fill. The high-potential.tertninaloiithe cathode load resistor N8 of the cathode follower is coupled through a resistors! 39 to the stabilizing network i 2 l, I22 of .the. blocking-oscillator .tube

lili.

A reactance tube 1 42 is 'coup'led'to the, resonant circuit i'l lii'il of the blocking oscillator through coupling condenser 1 H. 'ZIh'eaSimulated reactance introduced into the lbloclz'ingeoscillator resonant circuit by the reactance tube I iii. is controlled in accordance with thedetected modulation components available tic-he network I03, m9 oi the phase detector. This,.net-' WOl'k is connected to the input fcircuitbf reactance tube M0.

The output signal of the phase detector is supplied through the cathode vfollower .135 vto the audio-frequency amplifier .31 land sound-signal reproducing device 3-2.

In the operation of the high-level, phase -.detector of FigJSQthe detectorbecenter tunedlto the mean frequency of the frequencyrmodulated signal applied to terminals [2 5, 12 8. .Itlisthen v side-tuned in relation to the frequency .cf .Xthe phase-reference signal supplied hover the .ilink The blocking. oscillator vfl .115 .:ha'ssuch file/inning yani'es with the modulation ;-.components. control aeifects saugmentcone another -.to :estab- -'lifih' siibstcutiallyiixediapperentuphase relations 18 lthatlresidnalzoscillations. carry over from one oscillation-generatingperiod to the next, which means that (the blocking oscillator has hangover. I helblocking-actions in -the'phase detector FLOO-amdtheblocking oscillator i 15 are timed so .thatieachfoscillation interval of the phase detector HI flzistarts ibefore' butloverlaps an oscillation-gen- ;erating interval of the blocking oscillator H5, andthe oscillationsperiodically generated by the phase detector have a maximum amplitude of ithe sameiorder of magnitude as those generated by theblockingoscillator -l i 5.

.Having established the operating conditions zreferredito .lin lthejvpreceding paragraph, the op- ;eration, .l'ihetollvwalllilystem is as follows. (In ianysgiveneauench -.cycle of the phase detector iiflll, Ith'e,oscillationswhich are initiated have a .lphasarelated rto thatvof the frequency-modulated isignailsdurlng thezperiod- :of -maximum sensitivity .ofatheadetector. These oscillations, which start off-aha melati-vely low level, increase in amplitude exponentially. The maxi-mum amplitude level obtained visdimited by the diode limiter I38 .ai hich s'efie'c'titely adamps the phase detector. When 'lthessaturation interval is initiated in the blocking-oscillator, :a :strong pulse of blocking potential .is itsupplied wfrom the anode-cathode cinculit -thereofito the diode 1imiter, its. In this manner the diode ..limiter is disabled at a time whenithephaseereference:signal is being applied to -,the1.phase detector. The relative phase of ith82OSCfl1ati0DS then existing in the phase deteotOn-ascompared with :that of the phase-ref- 'erence;-:s'igna1 determines the rectification space currentvwhich flow-sun the tube Ills and hence lthe ltime required;to -discharge the condenser m5 and terminate the particular oscillation-generating periodiof the phase detector. In other words, th'ephase'icomparisonismadeat a time in each queneh oy'cle' o'f the phase detector when oscillations rare *beinggenerated with approximately saturation level amplitude. The duration of the saturation level interval of the phase detector in any quench cycle will-vary with the phase rela- "tionwofl-thersig nals compared during the phasecompanison interval, being :small when the compareds-ignalsare inrphase and increasing 'asthose 'SYEDHJSQ bECOmGJiQUt10f phase. The variations in the saturation-level intervals cause related changesiinithexquenchfrequency of the detector andg'ithere'fore, the average anode-cathode current i'o' thadetector reflectsthe modulation components 'o'f ithe .rrec'eived frequency modulated signal.

The-'output'signalof the'phase detector is not inl yi l'ltil'lzd win-"the audio-frequency system '35, 32 but aise controls the -bloc'king frequency of thebloking oscillaitor. "Adjustment of theblockin'g frequency of Fthe blo'ckin-g oscillator deterniines' the time atwhich thediode limiter its is =c'lis'abled and, therefore, the "time *at which the oscillations "0f the phase detector begin to increase toisaturation level amplitude. This is in the nature of a quench-frequency variation in a.=rsense Which tends to maintain substantially fixed apparent phase relationships between the compared. signals. I'I'he sametype-of phase contrdl isioccasioned'by the reactance tube-Mu which receives the signal output from the network Hi3 andal-ilssof thelphase detector, which output also The :li'etweexi ,thesfrcgnencyemodulated signal supplied 19' to terminals I27, I28 and thephase-reference signal supplied by oscillator II5.

One particular advantage of the high-level detector of Fig. 8 is that the limiter I30, by limiting the amplitude level of the oscillations in the phase detector prior to the instant of phase comparison, substantially eliminates the eifect of undesired amplitude modulation which may be superimposed on the applied'frequency-modulated signal.

The embodiment of Fig. 9 is similar to that of Fig. 8 and corresponding components thereof are identified by the same reference characters. In Fig. 9, however, the blocking oscillator II'5 supplies the quenching signal to "the superr'egenL erative phase detector. Since the phase detector i of the externally quenched type, it is not necessary to disable the diode limiter I30 in order to permit the oscillations in'the detector to achieve saturation-level amplitude because the termination of the negative-conductance interval of the phase detector is primarily under the control of the applied quench signal. Another difference between the arrangements of Fig. 8 and Fig. 9 resides in the fact that a quench-harmonic detector is utilized in the latter to derive an output signal from the phase detector representing the modulation components of the applied frequencymodulated signal. This detector is provided by a diode rectifier I50 coupled with'aload circuit, comprising a condenser I5I and a resistor I52, across the secondary winding of a double-tuned transformer I53. The stabilizing network I08, I 69 of the phase detector I includes the resistor I52 so that a bias may be applied therethrough from the quench-harmonic detector to the control electrode of the tube I00. The primary side of the double-tuned transformer I53 is included in the anode circuit of the tube I00 which is completed by a source of unidirectional potential +B, by-passed by acondenser I54. The transformer I53 is tuned to select a desired harmonic-frequency component of the quench frequency of the phase detector.

The blocking oscillator is included within the broken-line rectangle I 50 and has a blocking network I6I, I62 and a bias potential Ecassociated with its control electrode. A condenser I63 derives a quenching signal from the blocking network of the oscillator and supplies it to the input circuit of the tube I00 to effect super regenerative operation in the phaseidetector. The oscillatory frequency of the blockingaoscil lator is under the control of a reactance tube in'-= eluded within the broken-line rectangle I40.

The reactance tube is ofconventional design, including a vacuum tube I65 having its anode and control electrode coupled together through a condenser I86 and an inductor I6'I,.. The control electrode is connected to ground through resistors I68 and I69 and a condenser-H10. The simulated reactance introduced by-thereactance tube into the resonant circuit ,II6I20 of the blocking oscillator I60 through a coupling condenser I'II is varied in accordance with the, signal output of the quench-harmonic detector I50. To this end, the load impedance II, I52 of the quench-harmonic detector is coupled to the input circuit of the reactance tube through a resistor I72. I I This arrangement effects a phase comparison in essentially the same way as that described in connection with Fig. 8- and 'S:their -'opera-tion' is generally similar. Howeven -the-timihg of the oscillation intervals of-the' phase detector I00 relative to the'saturation intervals of the block.- ing oscillator IE0 is automatically established because the quench signal applied to the phase detector from the network I 6I I62 of the blocking oscillator initiates oscillations in the phase detector slightly in advance of the saturationlevel interval of the blocking oscillator. Consequently, when the blocking oscillator saturates, the oscillations of the phase detector have already achieved their maximum amplitude as de termined by the diode limiter I30. The use of the quench-harmonic detector I50 takes advantage of the fact that the average value of all the signal components included in the anode-cathode current of the phase detector varies in accordance with the phase relations present during the intervals of phase comparison. Therefore, while the modulation components may be obtained directly from the average current of the phase detector they may also be derived on the basis of the average value of a selected quench-harmonic component of that current. The control of the reactance tube I40 by the output signal of the quench-harmonic detector I50 adjusts the oscillatory frequency of the blocking oscillator 60 to tend to maintain a substantially fixed apparent phase relationship between the angular-Velocity-modulated signal and the phase-reference signal as observed in succeeding phase-comparison intervals of the phase detector.

In all the described modifications of this invention, the phase-reference signal is a continuous signal as already defined and the phase detector has sufiicient circuit damping that the oscillations generated in one quench cycle are suppressed to an insignificant value prior to the next succeeding oscillatory interval of the detector. Where low-level detection is practiced, the phase relations of the frequency-modulated signal and the phase-reference signal at the intervals of maximum sensitivity of the phase detector cause the average current of the detector to vary in accordance with the modulation of the frequency-modulated signal. For the high-level case, on the other hand, the phase comparison is made on the basis of the relative phase of the reference signal and the oscillations that have previously been established in the detector by the frequency-modulated signal and with a phase related" to that signal. Here, too, the average current of the detector varies with the phase relations during the phase-comparison intervals and hence represents the modulation components of the frequency-modulated signal.

In practicing the invention with arrangements of the type represented in Fig. 1, it is possible to realize the combined effects of low-level and high-level phase comparison. The low-level phase comparison of the received signal and the reference signal at the maximum-sensitivity period of any quench cycle determines the buildup time of the oscillations generated in that cycle. Where the reference signal has a suiiiciently high amplitude, it may determine the duration of the oscillation interval characteristic of high-level operation. These eiTects may augment one another and in any such case the arrangement utilizes the principles of both low-level and highlevel detection in deriving the modulation components-of the received signal. In some cases, it is preferred to have the detector center-tuned to thefrequency-modulated signal and sidetuned to the phase-reference signal as previously ex'plained- 'In each modification, the phase de- 21 tector has unusually high amplitude-modulation rejecting properties which is especially desirable in the reception of frequency-modulated signals for, in the absence of such properties, undesired amplitude modulation superposed on the received signal is undesirably derived and reproduced.

In discussing the several modifications of the invention, the expression apparent phase rela tion has been used to signify the phase relations of the modulated signal and the phase-reference signal at any comparison interval. These signals are not of the same frequency and consequently have no fixed phase relation. The expression apparent phase relation is intended to mean the relative phases of such signals at the observed interval.

While there have been described what are at present considered to be the prefered embodiments of this invention, it will beobvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. A system for receiving an angular-velocitymodulated wave signal having a given mean frequency comprising: an oscillation generator for supplying a continuous-phase reference signal having a frequency different from that of said mean frequency; a superregenerative wave-signal phase detector for utilizing said angular-velocitymodulated signal; and means for applying said phase-reference signal to said detector at least during a selected interval of each quench cycle of said detector; said detector being centertuned for signals of said mean frequency and being side-tuned for said phase-reference signal and responsive to both said last-mentioned signals during said selected intervals of said quench cycles to effect therein a phase comparison of said angular-velocity-modulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angularvelocity-modulated signal; said system including means responsive to the phase relations of said angular-velocity-modulated signal and said phase-reference signal during said intervals of phase comparison for controlling an operating characteristic of said system to tend to maintain a substantially fixed apparent phase relationship between said angular-velocity-modulated signal and said phase-reference signal.

.2. A system for receiving an angular-velocitymodulated wave signal having a given mean frequency comprising: an oscillation generator for supplying a continuous-phase reference signal having a frequency different from that of said mean frequency and having an effective intensity much greater than that of said angular-velocitymodulated signal; a superregenerative wavesignal phase detector for utilizing said angularvelocity-modulated signal; and means for applying said phase-reference signal to said detector at least during a selected interval of each quench cycle of said detector; said detector being centertuned'for signals of said mean frequency and being side-tuned for said phase-reference signal and responsive to both said last-mentioned signals during said selected intervals of said quench cycles to effect therein a phase comparison of said angular-velocity-modu1ated. signal and said phase-reference signal to develop an outputsignal having characteristic variations representing the modulation components of said angularvelocity-modulated signal; said system including means responsive to the phase relations of said angular-velocity-modulated signal and said phase-reference signal during said intervals of phase comparison for controlling an operating characteristic of said system to tend to maintain a substantially fixed apparent phase relationship between said angular-velocity-modulated signal and said phase-reference signal.

3. A system for receiving an angular-velocitymodulated wave signal having a given mean frequency comprising: an oscillation generator for supplying a continuous-phase reference signal having a frequency different from that of said mean frequency; a Superregenerative Wave-signal phase detector for utilizing said angular-velocity modulated signal and said phase-reference signal; and means for applying said phase-reference signal to said detector at least during a selected interval of each quench cycle of said detector; said detector being center-tuned for signals of said mean frequency and being side-tuned for said phase-reference signal and responsive to both said last-mentioned signals during said selected intervals of said quench cycles to effect therein a phase comparison of said angularvelocity-modulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular-velocitymodulated signal; said system including means responsive to the phase relations of said angularvelocity-modulated signal and said phase-reference signal during said intervals of phase comparison for controlling a, frequency characteristic of said system to tend to maintain a, substantially fixed apparent phase relationship between said angular-velocity-modulated signal and said phase-reference signal.

4. A system for receiving an angular-velocity. modulated wave signal comprising: an oscillation generator for supplying a continuous-phase reference signal; a superregenerative wave-signal phase detector for utilizing said angular-velocitymodulated signal; and means for applying said phase-reference signal to said detector at least during a selected interval of each quench cycle of said detector; said detector being responsive to said angular-velocity-modulated signal and said phase-reference signal during said selected intervals of said quench cycles to effect therein a phase comparison of said angular-velocitymodulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular-velocity-modulated signal; said system including means responsive to the phase relations of said angular-velocity-modulated signal and said phase-reference signal during said intervals of phase comparison for controlling the quench frequency of said detector to tend to maintain a substantially fixed apparent phase relationship between said angularvelocity-modulated signal and said phase-reference signal.

5. In a system for receiving an angular-velocity-modulated wave signal having a given mean frequency comprising: an oscillation generator for supplying a continuous-phase reference signal having a frequency different from that of said mean frequency; a superregenerative wave-signal phase detector of the self-quenching type for utilizing said angular-velocity-modulated signal and said phase-reference signal; and means :for applying said phase-reference signal to said .de tector at least during a selected interval of each quench cycle of said detector; said :cletector being center tuned for signals of said mean frequency and being side-tuned for said phase-reference signal and respomive to both said last-mentioned signals during said selected intervals of aid quench cycles to effect therein a phase comparison of said angular-velocityemodulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular-velocity-modidated signal; said detector including a self-quenching arrangement 'respon,

sive to the phase relations of said angulmr-veloc ity znodulated signal and said phase-reference signal during said intervals of phase comparison -for controlling the self-quench frequency of said detector to tend to maintain a substantially fixed apparent phase relationship between said angular-yelocity modulated signal and said phasereference signal.

6. .A system for receiving an angular-velocitymoclulated Wave signal comprising: an oscillation generator for supplying a continuous-phase reference signal; a super-regenerative wave-signal phase detector of the separately quenched type for utilizing said angular-ve1ocity moduiated signal; means for supplying a quench signal to said detector; and means :for applying said phasereference signal to said detector at least during a selected interval \Of each quench cycle of said detector; said detector being responsive to said angular-veloc'ity-modulated signal and said phase-reference signal during said selected intervals of said quench cycles to. effect therein a phase comparison of said angular-*velocity-modulated signal and said phase-reference signal. to develop an output signal having characteristic variations representing the modulation compo nents of said angular-velocity-modulated signal; said system including means responsive to the phase relations of said angular-velocity-modulated signal and said phase-reference signal during said intervals voi phase comparison for adlusting the fiequency .of said quench signal to tend to maintain :a substantially fixed apparent phase relationship between said angular-velocity-modulated signal and said phase-reie1ence signal.

7. A system tor receiving an angular-velocity modulated Wave signal comprising: anoscillation generator for supplying a continuous-phase reference signal; a super-regenerative wave-signal phase detect-or of the separately quenched type for utilizing said angular-velocity-modulated signal; means for dcriving from said oscillation'genorator and for applying to said detector a quench signal; and means for applyingsaid phase-reference signal to said detector at least :during a selected interval of each quench cycle of said detector; said detector being responsive to said angular-velocity-modulated signal and said p-haseweierence signal during said selected intervals of said quench cycles to eflect therein a phase comparison of said angular-velocity-modulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular velocity-modulated signal; said system including means responsive to the phase relations of said angular-veilocity-modulated signal and said phase-reference signal during said intervals of phase comparison for con- Ill trolling an operating characteristic of said oscillation generator to adjust the frequency of said quench signal to tend to maintain a substantially fixed apparent phase relationship between said angular-velocity-modu1ated signal and said phase-reference signal.

8. A system for receiving an angular-velocitymod-ulated wave signal comprising: a blocking oscillator having residual oscillations throughout each blocking interval for supp-lying a continunus-phase reference signal; a superregenerative wave-signal phase detector of the separately vcpienched type for utilizing said angular-velocitymodulated signal; means for deriving from said oscillator and for applying to said detector a periodic quench signal having a frequency corresponding to the blocking frequency of said oscillator; means for applying said phase-reference signal to said detector at least during a selected interval of each quench cycle of said detector; said detector being responsive to said angularvelocity-modulated signal and said phase-reference signal during said selected intervals of said quench cycles to effect therein a phase comparison of said angular-velocity-modulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular-velocity-modulated signal; and means for applying said output signal of said detector to said oscillator to adjust the blocking frequency thereof to tend to maintain a substantially fixed apparent phase relationship between said angular-velocity-modulated signal and said phasereference signal.

9. A system for receiving an angular-velocity- .modulated Wave signal having a given mean frequency comprising: an oscillation generator for supplying a continuous-phase reference signal having a frequency different from that of said mean frequency; and a superregenerative wavesignal phase detector for utilizing said angularvelocity-modulated signal and said phase-reference signal; means for applying said phase-reference signal to said detector at least during a selected interval of each quench cycle of said detector; said detector being center-tuned for signals of said mean frequency and being sidetuned for said phase-reference signal and responsive to both said last-mentioned signals during said selected intervals of said quench cycles to effect therein a phase comparison of said angular-velocity modulated signal and said phasereierence signal to develop an output signal having characteristic variations representing the 'modulation components of said angular-ve1ocitymodulated signal; and frequency-control means coupled to said generator and responsive to said output signal of said detector for controlling the requency of said phase-reference signal to tend to maintain a substantially fixed apparent phase relationship between asid :angular-velocity-mod ulated signal and said phase-reference signal.

10. A system for receiving an angular-velocitymodulatcd wavesignal having a given mean frequency comprising: an oscillation generator for supplying a continuous phase reference signal having a frequency different from that of said mean frequency; .a superregenerative wave-signal phase detector for utilizing said angular-velocitymodulated signal andsaid phase-reference signal: means for applying said phase-reference signal to said detector at least during a selected interval of each quenchrcycle of said detector; said detector .being center-tuned for signals of said mean frequency and being side-tuned for said phase-reference signal and responsive to both said last-mentioned signals during said selected intervals of said quench cycles to effect therein a phase comparison of said angular-velocitymodulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation com ponents of said angular-velocity-modulated signal; a reactance tube coupled to said generator for controlling the frequency. of said phasereference signal; and means for applying said output signal of said detector to said reactance tube to adjust the frequency of said phase-reference signal to tend to maintain a substantially fixed apparent phase relationship between said angular-velocity-modulated signal and said phase-reference signal.

11. A system for receiving an angular-velocitymodulated wave signal having a given mean frequency comprising: an oscillation generator for supplying a continuous-phase reference signal having a frequency diiferent from-that of said mean frequency; a super-regenerative Wave-signal phase detector, for utilizing said angularvelocity-modulated signal and said phase-reference signal, having a period of maximum sensitivity in each quench cycle; and means for applying said phase-reference signal to said detector at least during said maximum-sensitivity period of each quench cycle of said detector; said detector being center-tuned for signals of said mean frequency and being side-tuned for said phase-reference signal and responsive to both said last-mentioned signals during said selected intervals of said uench cycles to eiiect therein a phase comparison of said angularvelocity-modulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular-velocitymodulated signal; said system including means responsive to the phase relations of said angularvelocity-modulated signal and said phase-reference signal during said intervals of phase comparison for controlling an operating characteristic of said system to tend to maintain a substantially fixed apparent phase relationship between said angular-velocity-modulated signal and said phase-reference signal.

12. A system for receiving an angular-velocitymodulated wave signal comprising: an oscillation generator for supplying a continuous-phase reference signal; a super-regenerative wavesignal phase detector for utilizing said angularvelocity-modulated signal; and means for applying said phase-reference signal to said detector at least during a selected interval of each quench cycle of said detector; said detector being responsive to said angular-velocity-modulated signal and said phase-reference signal during said selected intervals of said quench cycles to effect therein a phase comparison of said angular-velocity-modulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular-velocity-mo-dulated signal; said system including means responsive to the phase relations of saidangular-velocitymodulated signal and said phase-reference signal during said intervals of phase comparison for controlling the quenching frequency of said detector and the frequencyof said-.phase-rei erence signal to tend to maintain a substantial- 1y fixed apparent phase relationship between 26 said angular-velocity-modulated signal and said phasereference signal.

13. A: system for receiving an angular-velocitymodulated Wave signal having a given mean frequency comprising: a blocking oscillator having residual oscillations throughout the blocking intervals between the generation of oscillations for supplying a continuous-phase reference signal having a frequency different from that of saidmean frequency; a superregenerative wavesi gnal. phase detector for utilizing said angularvelocity-modulated signal and said phase-reference signal and having a period of maximum sensitivity in each quench cycle occurring within an oscillation-generating period of said blocking oscillator; and means for applying said phasereference signal to said detector at least during ,said maximum-sensitivity period of each quench 'cycle of said detector; said detector being center-tuned for signals of said mean frequency and being side-tuned for said phase-reference; signal and responsive to both said lastmentioned signals during said selected intervals of said quench cycles to effect therein a phase comparison of said angular-velocity-modulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular-velocity-modulated signal; said system including means responsive to the phase relations of said angular-velocity-modulated signal and. said phase-reference signal during said intervals of phase comparison for controlling an operating characteristic of said system to tend to maintain a substantially fixed apparent phase relationship between said angular-velocitymodulated signaland said phase-reference signal.

14. A system for receiving an angular-velocitymodulated wave signal having a given mean frequency comprising: a blocking oscillator for supplying a continuous-phase reference signal having a frequency different from that of said mean frequency, said oscillator periodically generating oscillations of a high effective intensity compared to said angular-velocity-modulated signal and having residual oscillations throughout the intervals between the generation of oscillations; a superregenerative wave-signal phase detector for utilizing said angular-velocity-modulated signal and said phase-reference signal and having a period of maximum sensitivity in each quench cycle occurring within an oscillation-generating period of said blocking oscillator; and means for applying said phase-reference signal to said detector atleast during said maximum-sensitivity period of each quench cycle of said detector; said detector being center-tuned for signals of said mean frequency and being side-tuned for said phase-reference signal and responsive to both said last-mentioned signals during said selected intervals of said quench cycles to effect therein a phase comparison of said angularvelocity-modulated signal and said phase-re;- erence signal to develop an output signal having characteristic variations representing the modu-' lation components of said angular-velocity-rnodu lated signal; said system including means responsive to the phase relations of said angularvclocity-modulated signal and said phase-reference signal during said intervals of phase comparison for controlling an operating characteristic of said system to tend to maintain a substantially fixed apparent phase relationship between said angular-velocity-modulated signal and said phase-reference signal.

15. A; system for receiving an: angular-velocity: modulated Wave signal comprising: a Hocking oscillator for supplyin a; continuous-phase refrence signal, said oscillator periodically generating oscillations of a different frequency from and a high effective intensity compared to saidangular-velocity-modulated signal and having resid-' ual oscillations throughout the intervals between the generation of oscillations; a superregenerative wave-signal phase detector of the separately quenched type for utilizing said angular velocity modulated signal; means for deriving from: said oscillator and for applying to said detector a pcriodic quench signal having a" frequency correspendin to the blocking frequency" of said oscillator and having a time relation such that said detector exhibits maximum sensitivity in each quench cycle and Within each oscillation-generating period of said oscillator; means for applying said phase-reference signal to said detector at least during said maximum-sensitivity period of each quench cycle of said detector; said detector being responsive to said angular-velocityinodulated signal and said phase-reference signal durin said. maximum sensitivity periods to effect therein a phase comparison of said angular veloony-modulated signal and said phase-reference signal to develop" an output signal having characteristic variations representmg the modulation components of said angularwelocity-modulated signal; and means for utilizing said output signal of said detector to control the blocking frequency of said oscillator to tend to maintain a substantially fixed apparent phase relationship between said angular-velocity inodulated signal and said phase-reference signal 16. A system for receiving an angular-velocitymodulated Wave signal comprising: a blocking oscillator for supplying a continuous-phase reference signal, said oscillator periodically generating oscillations of a different frequency from and a high effective intensity compared to said angular-volecity-modulated signal and having residual oscillations throughout the intervals between the generation of oscillations; a reactance tube coupled to said oscillator to control the oscillatory frequency thereof; a superregenerative wave-signal phase detector of the separately quenched type for utilizing said. angular-velocitymodulated signal; means for deriving from said oscillator and for applying tosaid detector 3. periodic quench signal havingv a frequency corresponding to the blocking frequency of said oscillator and having a time relation such that said detector exhibits maximum sensitivity in each quench cycle and within each oscillation-generating period of said oscillator; means for applying said phase-reference signal to said detector at least during said maximum-sensitivity period of each quench cycle of said detector; and detector being responsive to said angu1ar-vel0citymodulated signal and said phase-reference signal during said maximum sensitivity periods to effect therein a phase comparison of said: aneu lar-velocity-modulated signal and said phase reference signal to develop an output signal hav ing characteristic variation's representing the modulation components of said angular-velocity modulated signal; and means for applying said output signal of said detector to said reactance tube and to said oscillator to control the oscillatory frequency and the blocking frequency of said oscillator to tend to maintain a substantially'fixed apparent phase relationship between said angu' lar vel'ocity moduiated signal and said hasereference signal.-

17. A system for receiving an angular-velocitymodulated wave signalhavlng a given mean irequency comprising: an oscillation generator for supplying a continuous-phase reference signal having a frequency different from that of said mean frequency; a saturation-mode superregenerative' wave-slgnal phase detector for utilizing said angular-velocity-modulated signal and said phase-reference signal and including means for phase relations of said angular-velocity-modulated signal and said phase-reierence signal during said intervals of phase comparison for controlling an operating characteristic of said system to tend to maintain a substantially fixed apparent phase relationship between said angu-Iar-velocity-modulated signal and said phase-reference signal. I

13. A system for receiving an angular-velocity modulated wave signal having a given mean fre I quency comprising: a blocking oscillator having residual oscillations throughout the blocking intervals between the generation of oscillations for supplying a continuous-phase reference signal having a frequency different from that of said mean frequency; a; saturation-mode superregenera-five wav'e signal phase detector for utilizing said angul'ar-vclocity-modulated signal and said phase-reference signal and including means for limiting oscillations generated therein to a value less than saturation-level amplitude, said detector havin periodically recurring oscillation intervals Whichindiv'idual-ly start before and overlap an oscillation-generating interval of said oscillator; and means for applying said phase-reference signet to said detector during oscillation intervals thereof; said detector being center-tuned for signals of said mean frequency and being sidetuned for said phase-reference signal and responsive' to both said last-mentioned signals during said selected intervals of said quench cycles to effect therein a phase comparison of said angular velocitwmodulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular-velocity-modulated' signal; said system including means responsive to the phase relations of said angularvelocity modul-atedsignal and said phase-referonce signal during said intervals of phase comparison for controlling an operating characteristicof said system to tend to maintain a substantially fixed apparent phase relationship between said angular-velocity-modulated signal and said phase reference signal.

1-9. A system for receiving an angular-velocitym/odulated wave signal having a givenmean frequency comprising: a blocking oscillator having residual oscillations throughout the blocking intervals between the generation of oscillations for supplying a continuous-phase reference signal means for limiting oscillations generated there in to a value less than saturation-level amplitude, I said detector being center-tuned to said m'ean frequency of said angular-velocity-modulated signal and side-tuned to said phase-reference signal and having periodically recurring oscilla i tion intervals which individually start before and overlap an oscillation-generating interval ofjJsaid oscillator; and means for applying said phase-f reference signal to said detector during oscilla- 7 tion intervals thereof; said detector beingretion intervals of said detector to effect therein a phase comparison of said angular-velocitymodulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular-velocity-modulated signal; said system including means responsive to the: phase relations of said angular-velocitymodulated signal and said phase-reference signal during said intervals of phase comparison for controlling an operating characteristic of said system to tend to maintain a substantially fixed apparent phase relationship between said angular-velocitymodulated signal and said phase-reference signal.

7 21'. A system for receiving an angular-velocitymodulated wave signal having a given mean fresponsive to said angular-velocity-modulated; sig-'- nal and said phase-reference signal duringgsaid' oscillation intervals of said detector to eiiect therein a phase comparison of said angula'r+ve locity-modulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular-velocity-modulated signal; said system including means' responsive to the phase relations of said angularvelocity-modulated signal and said phase-reierence signal during said intervals of phase comparison for controlling an operating characteristic of said system to tend to maintain a substantially fixed apparent phase relationship between said angular-velocity-modulated signal and said phase-reference signal.

20. A system for receiving an angular-velocity modulated wave signal having a given mean vfrequency comprising: a blocking oscillator having residual oscillations throughout the blockingin- I gular-velocity-modulated signal and including means for limiting oscillations generated therein to a value of the same order of magnitude as the oscillations generated by said oscillator: but less than saturation-level amplitude, said detector being center-tuned to said mean frequency 1 of said angular-velocity-modulated signalya'nd side-tuned to said phase-reference signal and having periodically recurring oscillation intervals which individually start before and overlap i an oscillation-generating interval of said later; and means for applying said phase-refer;

ence signal to said detector during oscillatiod in-if tervals thereof; said detector being responsive to said angular-velocity-modulated signal and said phase-reference signal during said oscilla- 5 phase-reference signal.

quency comprising: an oscillation generator for supplying a. continuous-phase reference signal having a frequency different from that of said mean frequency; a saturation-mode superregenerative wave-signal phase detector for utilizing said angular-velocity-modulated signal and said phase-reference signal and including means for limiting oscillations generated therein to a value less than saturation-level amplitude; means for applying said phase-reference signal to said detector during oscillation intervals thereof; said detector being center-tuned for signals of said mean frequency and being side-tuned for said phase-reference signal and responsive to both said last-mentioned signals during said selected intervals of said quench cycles to effect therein a phase comparison of said angular-velocitymodulated signal and said phase-reference signal to develop an output signal having characteristic variations representing the modulation components of said angular-velocity-modulated signal; and means for disabling said limiting means during said intervals of phase comparison; said system including means responsive to the phase relations of said angular-velocitymodulated signal and said phase-reference signal during said intervals of phase comparison .for controlling an operating characteristic of said system to tend to maintain a substantially fixed apparent phase relationship between said angular-velocity-modulated signal and said DONALD RICI-IMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,273,090 Crosby Feb. 17, 1942 2,363,651 Crosby Nov. 28, 1944 2,462,759 McCoy Feb. 22, 1949 

